SUNRISE 


AND  SUNSET 

IN  THE 

UNITED  STATES 


TIMES 

OF 

SUNRISE  AND  SUNSET 

IN  THE 

UNITED  STATES 

BY 

EGBERT  WHEELER  WILLSQJtf  Oi 

>\  '  .• 

Professor  of  Astronomy  in  Harvard  University  '•>,'>  Jv'>  ^  \  j  ,/, 


HARVARD  UNIVERSITY  PRESS 
CAMBRIDGE 


COPYRIGHT,    1908,   BY    ROBERT  W.  WILLSON 
ALL    RIGHTS    RESESVKD 


SUNRISE   AND   SUNSET 

The  upper  map  on  each  of  the  following  pages  is  to  be  used  for  finding 
the  standard  time  of  sunrise  for  the  date  printed  at  the  head  of  the  page, 
at  any  given  point  of  the  United  States ;  the  time  of  sunset  may  be  found 
from  the  lower  map. 

The  time  is  in  each  case  Central  Standard  Time  and  is  read  off  directly 
from  the  map  by  means  of  the  "time  lines  "  drawn  upon  it. 

The  line  "VI"  on  the  upper  map  is  drawn  through  all  those  points 
where  the  sun  rises  at  6  A.  M.  of  Central  Standard  Time,  and  the  number 
at  the  top  of  any  line  gives  the  standard  time  of  sunrise  at  all  places  OIK 
that  line.     The  time  thus  shown  is  the  instant  at  which  the*  sun's* upper 
edge  appears  to  be  exactly  on  the  horizon.  •   ,  ," >>t\ti  \\"  "».?  \**>  i 

The  following  rules  apply  to  both  maps  : 

Rule  1.  If  the,  point  for  which  the  time  of  sunrise  or  sunset  is  de- 
sired lies  exactly  on  one  of  the  time  lines,  the  required  Central  Time  is 
read  directly  from  the  upper  end  of  the  line. 

Rule  2.  //'  the  point  lies  between  two  lines  the  required  time  lies 
between  the  times  of  the  two  lines  and  proportionally  nearer  to  the  time 
of  the  nearer  line. 

Rule  3.  If  Eastern  Time  is  required  one  hour  must  be  added  to  the 
time  as  read  from  the  map.  For  Mountain  and  Pacific  times  subtract 
one  and  two  hours  respectively. 

The  process  will  be  best  explained  by  the  following  illustrative  examples, 
all  of  which  refer  to  places  whose  positions  are  marked  upon  the  map. 

On  the  sunrise  map  for  January  first  the  dot  which  represents  Spring- 
field, 111.,  lies  upon  the  line  of  7h.  20m.,  which  is  the  time  of  sunrise  at  that 
place  on  the  first  of  January  of  each  year.  On  the  same  date  the  time  of 
sunrise  at  Toledo,  0.,  is  exactly  7  o'clock,  and  at  Des  Moines,  la.,  7h.  40m. 
The  position  of  Springfield  on  the  sunset  map  for  the  same  date  is  just 

947442 


half  way  between  the  lines  of  4h.  40m.  and  4h.  50m.,  and  the  time  of  sun- 
set is  4h.  45m.  In  the  same  way  the  sun  sets  at  Toledo  at  4h.  15m.  and  at 
Des  Moines  at  4h.  55m. 

Chicago  on  the  sunrise  map  lies  about  eight  tenths  of  the  way  from  the 
7h.  10m.  to  the  7h.  20m.  line,  hence  by  rule  2  the  sun  rises  at  7h.  18m.  The 
lower  map  shows  that  sunset  is  at  4.31. 

By  the  same  method  we  find  that  at  Denver  the  sun  rises  on  the  first 
of  January  at  8.20  and  sets  at  5.46  ;  but  as  Denver  keeps  Mountain  Time 
rule  3  requires  the  subtraction  of  one  hour  from  these  times,  making  them 
7.20  and  4.46  respectively. 

At  San  Francisco  (Pacific  Time)  sunrise  and  sunset  are  at  7.25  and 
5.02  (two  hours  have  been  subtracted  as  required  by  rule  3). 

Rule  4.  If  no  map  is  given  for  the  date  in  question  take  the  time 
\frw&\$ffel/&Q](f  next  preceding,  and  also  from  the  map  next  following 
itl$$il%&i  date,,  (lThe  required  time  lies  between  the  two  values  thus  found, 
and  is  proportionally  nearer  to  that  for  the  nearer  date. 

To  illustrate  rule  4  we  may  find  the  time  of  sunset  at  Boston  on  Jan.  6 
as  follows : 

Jan.  1,       3.23  Central  or  4.23  Eastern  Time. 
Jan.  9,      3.30.       "        "  4.30        "         " 

The  difference  is  7  minutes  or  |-  minutes  per  day.  The  interval  from 
Jan.  1  to  Jan.  6  is  5  days,  and  we  must  add  5  X  |-  minutes  or  4J-  minutes 
to  the  time  for  Jan.  1,  giving  for  sunset  at  Boston  Jan.  6,  4h.  27m. 

The  lines  are  so  drawn  on  the  maps  as  to  be  correct  for  the  second 
year  following  a  leap  year  (1906,  1910,  etc.);  the  error  in  any  other  year 
does  not  reach  one  minute  except  in  the  following  cases  : 

In  leap  years,  from  Feb.  15  to  Feb.  29,  and  again  from  Aug.  15  to  Nov.  1, 
sunrise  is  later  and  sunset  is  earlier  than  the  time  found  by  the  maps. 
The  amount  is  less  than  half  a  minute  in  the  southern  part  of  the  country, 
but  rises  to  about  a  minute  at  the  northern  boundary. 


From  March  1  to  May  15  in  leap  years  sunrise  is  earlier  and  sunset 
is  later  by  one  minute  in  the  Northern  and  by  about  half  a  minute  in  the 
Southern  States. 

Upon  each  map  are  shown  by  small  dots  all  cities  having,  in  1900,  a 
population  of  more  than  twenty-five  thousand,  except  where  confusion 
would  result  from  their  closeness  to  each  other.  The  state  capitals  are 
represented  by  somewhat  larger  dots. 

To  use  the  maps  for  any  place  not  so  indicated,  it  is  best  actually  to 
place  a  dot  in  its  proper  position  on  the  map. 

If  the  latitude  and  longitude  are  known,  the  dot  may  be  inserted  by 
means  of  the  "auxiliary  map"  following  the  maps  of  Dec.  31. 

For  this  purpose  put  a  small  piece  of  transparent  paper  on  the  auxiliary 
map  and  trace  the  outline  of  the  state.  Put  the  dot  in  its  proper  place  by 
means  of  the  lines  of  latitude  and  longitude.  Then  apply  the  tracing  to 
each  of  the  dated  maps  in  turn,  fitting  it  to  the  state  lines  as  closely  as 
possible,  and  press  on  the  dot  with  the  point  of  a  pencil  hard  enough  to 
make  a  dent ;  remove  the  tracing  and  put  an  ink  dot  in  the  depression. 

To  most  persons  these  maps  will  appeal  merely  as  a  curiosity,  but  they 
may  sometimes  serve  a  useful  purpose  in  finding  the  error  of  a  watch  where 
it  is  possible  to  note  the  time  of  sunrise  or  sunset  over  a  body  of  water  so 
extensive  that  its  visible  limit  appears  to  meet  the  sky,  but  in  comparing 
the  time  actually  observed  with  the  time  found  from  the  map  it  should  be 
remembered  that  in  the  United  States  to  a  person  130  feet  above  the 
water  level  the  sun  appears  above  the  horizon  a  full  minute  earlier  and 
sets  a  full  minute  later  than  if  the  observer  were  at  the  water's  edge.  At 
heights  of  500, 1200,  2100,  3300  feet  the  difference  amounts  to  2,  3,  4,  5 
minutes  respectively. 


JANUARY  FIRST 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


JANUARY  NINTH 


SUNRISE 

CENTRAL  STANDARD  Tl 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


MEXICO 


JANUARY  SEVENTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


JANUARY  TWENTY-FIFTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


IX 


SUNSET 

CENTRAL  STANDARD  TIME 


FEBRUARY  SECOND 


CENTRAL 


SUNRISE 

STANDARD  TIME- 


SUNSET 

CENTRAL  STANDARD  TIME 


FEBRUARY  TENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


FEBRUARY  EIGHTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


VII 

MEXICO 


FEBRUARY  TWENTY-SIXTH 


SUNRISE 

CENTRAL   STANDARD   TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


VIII 


MEXICO  vu 


MARCH  SIXTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VII 


.SUNSET 

CENTRAL  STANDARD  TIME 


VIII 


MARCH  FOURTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VIII 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


VIII      I  / 


MEXICO 


MARCH  TWENTY-SECOND 


SUNRISE 

CENTRAL  STANDARD  TIME 


VW 


SUNSET 

CENTRAL  STANDARD  TIME 


VIII 


MARCH  THIRTIETH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


VIII 


APRIL  SEVENTH 


SUNRISE 

CENTRAL  STANDARD  Til 


SUNSET 

CENTRAL  STANDARD  TIME 


VIII 


APRIL  FIFTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


W; 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


APRIL  TWENTY-THIRD 


SUNRISE 

CENTRAL   STANDARD   TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


MEXICO 


MAY  FIRST 


SUNRISE 

CENTRAL  STANDARD  TIME 


VII 


SUNSET 

CENTRAL  STANDARD  TIME 


40        30 


MAY  NINTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VII 


VII 


SUNSET 

CENTRAL  STANDARD  TIME 


MAY  SEVENTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


MAY  TWENTY- FIFTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


JUNE  SECOND 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


JUNE  TENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


JUNE  EIGHTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


JUNE  TWENTY- SIXTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


JULY  FOURTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VII 


MEXICO 


to 


SUNSET 

CENTRAL  STANDARD  TIME 


IX 


JULY  TWELFTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VII      \ 


VII 


SUNSET 

CENTRAL  STANDARD  TIME 


MEXICO 


JULY  TWENTIETH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VII        V 


SUNSET 

CENTRAL  STANDARD  TIME 


MEXICO         / 


JULY  TWENTY-EIGHTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VII 


SUNSET 

CENTRAL  STANDARD  TIME 


VIII 

MEXICO 


AUGUST  FIFTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL   STANDARD   TIME 


AUGUST  THIRTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


AUGUST  TWENTY-FIRST 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


AUGUST  TWENTY- NINTH 


SUNRISE 

CENTRAL   STANDARD   TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


V/// 


MEXICO 


SEPTEMBER  SIXTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


w// 


VII 


SEPTEMBER  FOURTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


SEPTEMBER  TWENTY-SECOND 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


SEPTEMBER  THIRTIETH 


SUNRISE 

CENTRAL  STANDARD  TIME 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


w// 


OCTOBER  EIGHTH 


SUNRISE 

CENTRAL   STANDARD   TIME 


vin 


SUNSET 

CENTRAL   STANDARD   TIME 


MEXICO 


OCTOBER  SIXTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


OCTOBER  TWENTY-FOURTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VIII 


SUNSET 

CENTRAL  STANDARD  TIME 


Vi! 


NOVEMBER  FIRST 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


VII 


NOVEMBER  NINTH 


SUNRISE 

CENTRAL   STANDARD   TIME 


VIII 


SUNSET 

CENTRAL 


\\\ 


VII 


NOVEMBER  SEVENTEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


CE 


SUNSET 

•NTRAL  STANDARD  TIME 


VII 


MEXICO 


NOVEMBER  TWENTY-FIFTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


VIII 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


DECEMBER  THIRD 


SUNRISE 

CENTRAL  STANDARD  TIME 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


DECEMBER  ELEVENTH 


SUNRISE 

CENTRAL   STANDARD   TIME 


IX 


MEXICO 


SUNSET 

CENTRAL  STANDARD  TIME 


DECEMBER  NINETEENTH 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


VII      \ 


DECEMBER  TWENTY-SEVENTH 


CENTRAL 


SUNRISE 

STANDARD   TIME 


MEXICO 


SUNSET 

CENTRAL  STANDARD 


DECEMBER  THIRTY-FIRST 


SUNRISE 

CENTRAL  STANDARD  TIME 


SUNSET 

CENTRAL  STANDARD  TIME 


VII 


AUXILIARY  MAPS 

130  125  120  115          "°          I05          ,IO°         ,9.5          ,9°  ,8.5  8.°,       .  ,7.5.  7°  6.5-. 

pspffiwftSiiiisww^^ 


--*-&-. 


--full 


JvtiK 


35 


30 


TTTT 
fcteter 


35 


ioo  95  90  85  80  75 


H5  no 


STANDARD   TIME   BELTS 


MEXICO 


Hifcerstoc 


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DUE  AS  STAMPED  BELOW 


JULSQ1998 


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LD  21-100m-7,'40 (6936s) 


VD  04998 


947443 


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